Technicaltraining. Productinformation. F48Powertrain
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ThisdocumentbasicallyrelatestotheEuropeanversionofleft-handdrivevehicles.Someoperating elementsorcomponentsarearrangeddifferentlyinright-handdrivevehiclesthanshowninthe graphicsinthisdocument.Furtherdifferencesmayariseasaresultoftheequipmentspecificationin specificmarketsorcountries.
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Informationstatus:June2015 BV-72/TechnicalTraining F48Powertrain Contents
1. DriveVariants...... 1 1.1. Model...... 2 1.2. Enginedesignation...... 3 1.2.1. Engineidentification...... 3
2. CoolingSystem...... 4 2.1. Coolingmodule...... 4
3. AutomaticTransmission...... 6 3.1. Designation...... 8 3.2. Functiondiagram...... 9 3.3. Ratios...... 10 3.4. Directshifting...... 11 3.5. Coastinginidle...... 11 3.6. LaunchControl...... 11 3.6.1. Activationoflaunchcontrol...... 12 3.7. ConnectedShift...... 12 3.7.1. Characteristicsandavailability...... 12 3.8. NotesforService...... 13 3.8.1. Specialtools...... 13 3.8.2. Manuallyunlockingthedrivepositionlock...... 13 3.8.3. Availablereplacementparts...... 14
4. xDrive...... 15 4.1. Introduction...... 15 4.1.1. Comparisonofall-wheeldrivesystems...... 15 4.2. Systemcomponents...... 17 4.2.1. Angulargearbox...... 18 4.2.2. Propellershaft...... 20 4.2.3. Rearaxledifferential...... 23 4.2.4. Systemwiringdiagram...... 26 4.3. Function...... 27 4.3.1. Longitudinaltorquedistribution...... 27 4.3.2. Operatingstrategy...... 29 4.4. NotesforService...... 30
5. OutputShaft,Front...... 31
F48Powertrain 1.DriveVariants
TheF48isavailablewithxDrive.Thefollowinggraphicshowsthelayoutofthatversion.
F48Drive
IntheF48acompletelynewdriveunitisused,whichfitsperfectlywiththespatialfunctionalconcept oftheBMW X1thankstoitsmodel-specificdesign.
ThenewBMWX1xDrive28iisoneofthefirstvehiclesofBMWwhichwillbedrivenbythebrandnew 4-cylinderengine.Itisapartofthenewlydevelopedmodularenginefamily.Itisalightweight,powerful andeconomicalengine,whichisequippedwithBMWTwinPowerTurbotechnology.
Specialfeatures
• New4-cylinderengines • Enginewithtransversemounting • xDrive • AllenginessatisfytheexhaustemissionstandardsSULEV
1 F48Powertrain 1.DriveVariants
Thefollowinglistshowstheadvantagesofthedifferentdriveconcepts(forvehicleswithafront engine):
Front-wheeldrive Rear-wheeldrive
• Thedriveunitiscomparativelycompact • Smallturningcirclepossible,asno andisintegratedbetweentheaxle rearviewofthedriverequiredwiththe mounting,steeringandfootwell. steeredfrontaxle. • Largeandvariablespatialoffering • Noannoyingdriveinfluencesinthe thankstoreductionordeletionof steering. thetransmissiontunnelandrearaxle • Goodpowertransmissiontothe differential. roadwayduringacceleration,asthe • Weightandcostreductions,dueto drivenaxleisloaded(primarilywhen deletionofpropellershaftandrearaxle drivingoffoninclines). differential,aswellasintegrationofthe • Balancedaxle-loaddistribution differentialinthetransmission. possible. • Goodtractiononsmoothroadway, • Excellentdynamiccorneringbehavior. independentoftheloadstatusofthe vehicle,duetohigheraxleloadatthe drivenaxle. • Reasonablebehaviorintheevent ofahead-oncollision(engineand transmissionintrudethepassenger compartmentless).
1.1.Model
ThefollowingmodelisofferedforthemarketintroductionoftheF48:
Model BMW228i Engine B46A20O0 Cylinders 4 Displacement [cm³] 1998 Power [kW(HP)] 170(231) Torque [Nm] 350 Automatictransmission GA8F22AW Manualgearbox –
2 F48Powertrain 1.DriveVariants
1.2.Enginedesignation
Inthetechnicaldocumentation,theenginedesignationisusedtoensureunambiguousidentification oftheengine.InthefollowingtabletheenginedesignationsusedintheF48areexplained.
Position Meaning Index Explanation 1 Enginedeveloper B BMWGroup 2 Enginetype 4 4-cylinderin-lineengine 3 Changetothebasic 8 Turbo-Valvetronicdirectinjection(TVDI) engineconcept 4 Workingmethodorfuel A Petrolengine,transversalinstallation andinstallationposition 5 + 6 Displacementin1/10 liter 20 2.0 litersdisplacement 7 Performanceclass U Lower M Middle O Upper 8 Revisionrelevantto 0 Newdevelopment approval 1 – 9 Redesign
1.2.1.Engineidentification
The7-digitengineidentificationisonthecrankcase.Thefirst6digitsoftheengineidentificationare deducedfromtheenginetype.Onlytheseventhdigitisdifferent.Withtheengineidentificationthe testnumberofthetypeapprovalcertificationislocatedatthe7thposition.
3 F48Powertrain 2.CoolingSystem
2.1.Coolingmodule
F48coolingsystemforB48engine
Index Explanation 1 Expansiontank 2 Electriccoolantpump 3 Coolingmodule 4 Coolingmodulebearing,top 5 Coolingmodulebearing,bottom 6 Coolantpump 7 Engineoil-to-coolantheatexchanger
AframelesscoolingmoduleisinstalledintheF48.Thisismadepossiblebyaconceptwithdifferent separationpointsbetweenradiatorandchargeaircooler,using,jointinterfacesforbodyandcoolant hoses.
Invehicleswithanautomatictransmission,atransmissionoil-coolant-heatexchangerisalsoflange- mountedatthetransmission.Thisissuppliedwithcoolantviathecrankcaseandadaptedcoolant hoses.
Inthefollowingdiagramyouseetheconnectionofthecoolingmoduleatthecoolingcircuitusingthe exampleoftheB46engine.
4 F48Powertrain 2.CoolingSystem
F48coolingcircuit,B46engine
Index Explanation 1 Radiator 2 Electricfan 3 Electriccoolantpump 4 Thermostat 5 Coolantpump 6 Exhaustturbocharger 7 Heatexchanger 8 Coolantshutoffvalve 9 Transmissionoil-to-coolantheatexchanger 10 Engineoil-to-coolantheatexchanger 11 Expansiontank
5 F48Powertrain 3.AutomaticTransmission
F48automatictransmission
IntheF48anew8-speedautomaticgearboxGA8F22AWareused:
Designation Gears Transferabletorque Useinengine GA8F22AW 8-speed 350 Nm B46A20O0
6 F48Powertrain 3.AutomaticTransmission
Theexcellentefficiencywasabletobeachievedbythefollowingmeasures:
• Smalloilpump • Lowertransmissionoilmainpressure • Optimallubricatingoilquantity • Transmissionoilwithlowviscosity • Largesteeringaxisinclination • Veryaccuratecontrolofthemultidiscconverterlockupclutchatlowloads bythree-lineactivation • Designedforautomaticenginestart-stopfunction(thereisalsoanelectricoil pumpinthehydraulicblockinordertomaintaintheminimumoilpressure) • Designedforidlespeedcoasting
Goodrideandshiftingcomfortwasabletoberealizedwiththefollowingmeasures:
• Newlydevelopedmechanicaltorsionalvibrationdamper • Efficienthydraulicswithnewvalves • Efficientclutchandbrakecontrol • Excellentdirectshiftingcapability(multipledownshifts,explainedinthefollowing)
IntheSportprogramandManualmodetheshiftpointandshiftspeedhaveamoresportydimension.
F48EGS,8-speedautomatictransmission
TheelectronictransmissioncontrolislocatedintheF48onthetransmissionhousing.Theselector leverpositionswitchisdesignedasahalleffectsensorandintegratedintheEGS.Theouterwiring betweenEGS,selectorleverpositionswitchandtransmissionwasdiscontinued,wherebythe susceptibilitytofaultswasalsoreduced.
7 F48Powertrain 3.AutomaticTransmission
3.1.Designation
Thetransmissiondesignationinthetechnicaldocumentationallowsittobeuniquelyidentified. Infrequentcases,however,onlyashortdesignationisused.Thisshortformisusedsothe transmissioncanbeassignedtoatransmissionfamily.TheGA8HPtransmissionfamily,consisting ofseveraltransmissionssuchastheGA8HP45Z,theGA8HP70ZandtheGA8HP90Z,isoften mentioned.
Position Meaning Index Explanation 1 Designation G Transmission 2 Typeoftransmission A Automatictransmission 3 Numberofgears 8 Eightforwardgears 4 – 7* Individual HP Hydraulicplanetarygear designations* L DesignationofGeneralMotorsPowertrain R DesignationofGeneralMotorsPowertrain 19 300 Nmgasengine F21A DesignationofAISINWarner 26 600 Nm 32 720 Nm 45 450 Nm (Zahnradfabrik350 Nm Friedrichshafen)700 Nm 45 900 Nm (General 390 Nm,4th gear410 Nm, Motors Powertrain) 70 90 390 8 Manufacturer A AISIN G Getrag J Jatco K GKN R GeneralMotorsPowertrain Z ZahnradfabrikFriedrichshafen H In-housepart
*Numbers4–7serveforindividualdesignation.Atransmissionvariant,size,transferabletorqueand technicalupdatecanberepresentedhere.
8 F48Powertrain 3.AutomaticTransmission
3.2.Functiondiagram
Functiondiagramusingtheexampleofa6-speedautomatictransmission
9 F48Powertrain 3.AutomaticTransmission
Index Explanation B1 BrakebandB1(blocksthefrontsungearoftherearplanetarygearset) B2 BrakeclutchB2(blockstheplanetcarrieroftherearplanetarygearset) C1 DriveclutchC1(connectstheplanetcarrierofthefrontplanetarygearsetto therearsungearoftherearplanetarygearset) C2 DriveclutchC2(connectstheintermediateshafttotheplanetcarrierofthe rearplanetarygearset) C3 DriveclutchC3(connectstheplanetcarrierofthefrontplanetarygearsetto thefrontsungearoftherearplanetarygearset)
3.3.Ratios
GA8F22AW Ratio,1stgear 5.25 Ratio,2ndgear 3.029 Ratio,3rdgear 1.95 Ratio,4thgear 1.457 Ratio,5thgear 1.221 Ratio,6thgear 1 Ratio,7thgear 0.809 Ratio,8thgear 0.673 Ratio,reversegear 4.015
10 F48Powertrain 3.AutomaticTransmission
3.4.Directshifting
WiththenewautomatictransmissionoftheF48,inmostcasesdirectshiftingtothedesiredgearis possible.Thisalsoappliesifgearsareskipped.
Adirectgearchangeisalwayspossibleifthestatushastochangeforoneoftheswitchedclutches orbrakes.Otherwise,atwo-stagegearchangeisperformed.However,ingeneralthecustomerdoes notnoticethisduetotheoptimizedtransmissioncontrolunit.
Thefollowingtableshowstheswitchedbrakesandclutchesforeachgearusingtheexampleofthe GA6F21AW.
Gear Brake Brake Clutch Clutch Clutch B2 B1 C2 C1 C3 N X 1 X X 2 X X 3 X X 4 X X 5 X X 6 X X Rw X X
Examples:
• Directshiftispossiblefrom4thto2ndgear,astheclutchC1doesnothavetobeshifted. • Directshiftisnotpossiblefrom5thto2ndgearasboththebrakeB1andtheclutchC1 havetobeswitched.
3.5.Coastinginidle
FortheF48the"Coastinginidleposition"functionisavailable.Undercertainprerequisitestheengine isautomaticallydisconnectedfromthetransmissioningearselectorswitchpositionD.Theengine runshereatidlespeed.
Furtherinformationon"Coasting"isavailableintheproductinformationbulletin"F01/F02LCI DisplaysandOperation".
3.6.LaunchControl
ForvehicleswithSportsautomatictransmission(SA 2TB),launchcontrolenablesoptimalacceleration whendrivingoff.Forcedupshiftsarealsoperformedwithoutareductionoftheenginetorque.This enablesadditionalaccelerationduringthegearshifts.
Inordertoavoidprematurecomponentwear,thedrive-offwithlaunchcontrolisonlyavailable100 timesovertheservicelifeoftheSportsautomatictransmissionandcannotberesetbyService.
11 F48Powertrain 3.AutomaticTransmission
3.6.1.Activationoflaunchcontrol
Step Responsibility 1 PresstheDSC buttonandselectSPORTusingthedrivingexperienceswitch. –IntheinstrumentclusterTRACTIONisdisplayedincombinationwithSPORT. TheindicatorlightDSCOFFilluminates. 2 Engagedriveposition S. 3 Firmlypressthebrakeusingtheleftfoot. 4 Presstheacceleratorpedalbeyondtheresistanceatthekick-downpressurepoint andhold. –Flagsymbolappearsintheinstrumentclusterandtheenginespeedforpulling awayisadjusted. 5 Releasethebrakewithin3secondsandholdtheacceleratorpedal. –Vehicleacceleratesoptimally.
3.7.ConnectedShift
ConnectedShiftusesnavigationdataforaforward-thinkingshiftstrategyoftheautomatic transmission.If,forexample,asharpbendisdetected,theautomatictransmissionshiftsdownearly andthegearisretainedinthebend.
Therouteguidanceofthenavigationsystemdoesnotneedtobeactivatedforthefunction.However, theidentificationofaturn-offrequest,forexamplebytheactiverouteguidanceoroperatingtheturn indicator,helpstocontrolthesystemmoreaccurately.Up-to-datenavigationmapdataalsoinfluences thecontrolaccuracy.
3.7.1.Characteristicsandavailability
InSPORTandCOMFORTmodes,thecharacteristicsofConnectedShiftareadaptedtotherespective drivingprogram,inECOPROmodeConnectedShiftisnotavailable.ConnectedShiftisalsonot availableduringcontroloperationofcruisecontrol.
ConnectedShiftisusedintheF48,dependingontheequipment,specificallyinvehicleswithgas engine,automatictransmissionandnavigationsystem.
Aprerequisiteisthatthemapdataandtherequiredadditionalinformationforthecountryareavailable. Thisisdependentonthenavigationmapproviderandisnotavailableworldwideforallcountries.
12 F48Powertrain 3.AutomaticTransmission
3.8.NotesforService
3.8.1.Specialtools
Twonewdiagnosticcablesweredesignedfortheautomatictransmissionasspecialtools:
• Adaptercable15-pin:83 30 2 352 734 • Adaptercable33-pin:83 30 2 352 718
3.8.2.Manuallyunlockingthedrivepositionlock
F48Manuallyunlockingthedrivepositionlock
Ifthegearselectorswitchisblockedinselectorleverposition Pdespitetheignitionbeingswitched on,brakebeingappliedandtheUnlockbuttonbeingpressed,thedrivepositionlockcanbemanually unlocked.Thereisareleaseleverunderthesleeveforthegearselectorswitch,whichcanbeoperated usingthescrewdriverfromthetoolkit,forexample.
13 F48Powertrain 3.AutomaticTransmission
3.8.3.Availablereplacementparts
Thefollowingcomponentsoftheautomatictransmissionarecreatedasreplacementpartsinaddition tovariousretainingandsealingelements:
• Cableholder(attransmissionhousing) • Gearshiftlever(atgearshiftshaft) • Electronictransmissioncontrol(EGS) • Oilfillerplug • Electricalwiringset • Gearboxinput-speedsensor • Hydraulicshiftunit • Cover(hydraulicshiftunit) • Transmissionoilcooler • Oildrainplug(withoverflow) • Torqueconverter • Radialshaftsealsfortransmissioninputshaft, aswellasleftandrightaxleshaft
14 F48Powertrain 4.xDrive
4.1.Introduction
Theall-wheeldrivesystemintheF48wasredevelopedandforthefirsttimeatBMW.Althoughthis all-wheeldrivesystemisalsocalledxDrive,itisconsiderablydifferentfromtheversionspreviously installed,whichwerebasedonarear-wheeldrive.
ThedifferencesofthexDriveversionsarelistedinthefollowingsection.
4.1.1.Comparisonofall-wheeldrivesystems
Thefollowinggraphicshowstheall-wheeldrivesystemoftheF48comparedtotheF25.
Comparisonoftheall-wheeldrivesystem:F25–F48
Index Explanation A Four-wheeldriveF25 B Four-wheeldriveF48 1 Frontaxledifferential 2 Automatictransmission
15 F48Powertrain 4.xDrive
Index Explanation 3 Transferbox 4 Rearaxledifferential 5 Angulargearbox 6 Longitudinaltorquedistribution(integratedintherearaxledifferential)
Thefollowingtableshowsthekeydifferencesoftheall-wheeldrivesystemsintheF25andintheF48.
F25 F48 Longitudinaltorque DSC DSC distributionrequirement (setpointtorque) Controlofthelongitudinal VTGcontrolunit Longitudinaltorque torquedistribution distributioncontrolunit Longitudinaltorque Multidiscclutch Multidiscclutchofthe distribution inthetransferbox longitudinaltorquedistribution Drivetorquewhen 100 %atrearaxle 100 %atfrontaxle multidiscclutchopen Activationofmultidisc Viaelectricmotorandballramp ViaEHPSandhydraulic clutch operatingpressure
Thenewall-wheeldrivesystemwithlongitudinaltorquedistributionclutchhasthefollowing advantagesincomparisontotheall-wheeldrivesystemwithtransferbox:
• Lowspacerequirement • Lowweight • Lowsplashinglossesinthemultidiscclutch(thanksto"Efficientmode")
• CO2reduction
16 F48Powertrain 4.xDrive
4.2.Systemcomponents
F48overviewoffour-wheeldrive
Index Explanation A Drivingpowertotherearwheels B Drivingpowertothefrontwheels 1 Frontwheel 2 Outputshaft,front 3 Angulargearbox 4 Automatictransmission 5 Propellershaft
17 F48Powertrain 4.xDrive
Index Explanation 6 Rearwheel 7 Outputshaft,rear 8 Crossmember 9 Rearaxledifferential(withintegratedlongitudinaltorquedistribution)
WithxDrivesomeofthisdrivingpoweristransmittedtotherearoutputshafts(7)viatheangular gearbox (3),thepropellershaft (5)andtherearaxledifferential (9).Thegearratiointheangular gearboxis1.74 : 1andintherearaxledifferential1 : 1.74.
Theenginespeedisincreasedand,atthesametime,thetorqueisreduced,asaresultoftheratio intheangulargearbox.Thepropellershaftcanthereforebedesignedwithsmallerdimensions.The weightreductionhelpsthefuelconsumptionandthefewermovingmassesbenefitthesmooth running.
Intherearaxledifferentialtheratioisthenreversed,sothatthesameenginespeedisappliedtothe frontandrearoutputshafts.
4.2.1.Angulargearbox
F48Angulargearbox
Index Explanation A Drivingpowertotherearwheels B Drivingpowertothefrontwheels 1 Angulargearbox 2 Pinionshaft
18 F48Powertrain 4.xDrive
Index Explanation 3 Inputshaft(hollowshaft)withcrownwheel 4 Intermediateshaft 5 Outputshaft,frontright 6 Propellershaft
Theangulargearboxislocatedbehindtheengineandissecuredattheautomatictransmissionandat thecrankcase.Ittransmitssomeofthedrivingpowertothepropellershaftandisdesignedasasingle- stage,i.e.onlyhasonefixedratio.
Theinputshaftoftheangulargearboxisdesignedasahollowshaftandisconnecteddirectlytothe differentialhousingofthefrontaxledifferential.Thedrivingpoweristransmittedfromthedifferential housingtothepropellershaftviathehollowshaft,thecrownwheelandthepinionshaft.
Asapowerinterruptionintheangulargearboxisnotpossible,thepropellershaftisdriven continuouslyviathepinionshaftduringthejourney.
Irrespectiveofthis,theintermediateshaftisguidedtothefrontrightoutputshaftthroughthehollow shaftandthecrownwheelintheangulargearbox.
19 F48Powertrain 4.xDrive
4.2.2.Propellershaft
F48propellershaft
Index Explanation A Connectiontorearaxledifferential viaflexibledisc B Connectiontoangulargearboxviaafixedballjointwithflangeandinlaynut C Propellershaftcenterbearingwithtripodjoint 1 Inlaynut 2 Shiftunit 3 Hexagonhead(forslackeningtheinlaynutattheangulargearbox)
20 F48Powertrain 4.xDrive
Thepropellershaftisresponsiblefortransmittingdrivingpowerprovidedbytheangulargearboxinthe formoftorqueandenginespeedtotherearaxledifferential.Withhelpofthetripodjoint,itoffsetsthe deflectionangleandlinearvariationsresultingfromtheassemblymovements.
Infrontofthepropellershaftcenterbearingisahexagonhead (3),atwhichthepropellershaftcanbe rotated.Asaresult,forleft-handdrivevehiclesthereistheoptiontoremovethepropellershaftfrom theangulargearbox,iftheinlaynut(1)isheldovertherightwheelarchatthesametime.
IntheF48withfour-wheeldrive,thecurrentlylongestpropellershaftofallcurrentBMWmodelsis installed.Itis2.2 mlong.Itisdesignedasatwo-piecetubularshaftandissecuredtothebodyinthe areaofthemiddlejointviatheflexiblecentermount.
Thepropellershaftcanbebentamaximumof10°.Otherwise,thegaiterinthetripodjointwillincur damage
Supportthepropellershaftduringremovalandinstallationandsecurethegaiterwithanti-kink protection.Itisimperativethecurrentrepairinstructionsareobservedwhenworkingatthepropeller shaft.
F48Shiftunitofthepropellershaft
21 F48Powertrain 4.xDrive
Index Explanation 1 Outerpipe(indirectionoftravel,rear) 2 Shiftunit 3 Innerpipe(indirectionoftravel,front) 4 Coating(toachieveadefinedlowstaticfrictionforce) 5 Shiftdirection
Inthefrontpropellershaftsections,twocontouredpipesectionsareinsertedinoneanother. Thecontourofthetwopipesectionsmeansitispossibletotransferthedrivetorque.Inaddition,the twopipesectionscanbeadjustedtowardseachother,wherebyacoatinggeneratesadefinedfriction forceof20 kN.
Intheeventofafront-endcollision,acounterforceofmaximum20 kNisgenerated,sothatan additionalloadpathisnotcreated.
Followinganaccident,theshiftunitofthepropellershaftmustbechecked.Ifthetwopipesections haveshiftedintooneanother,thepropellershaftmustbereplaced.Thecriteriaforcheckingand replacingspecifiedintherepairinstructionsaretobecompliedwithprecisely.
22 F48Powertrain 4.xDrive
4.2.3.Rearaxledifferential
F48Rearaxledifferential
Index Explanation 1 Bearing(rearaxledifferentialtorearaxlesupport) 2 Rearaxledifferential 3 Crossmember 4 Bearing(crossmembertobody)
TherearaxledifferentialintheF48withfour-wheeldriveissecuredatthefronttotherearaxlesupport andatthereartoanadditionalcrossmember.Inordertodecouplenoisesandvibrationsofthedrive trainfromthevehiclebody,boththerearaxledifferentialattherearaxlesupport,andtheadditional crossmemberatthebody,aresecuredviarubbermountings.
23 F48Powertrain 4.xDrive
Longitudinaltorquedistribution
F48Longitudinaltorquedistribution
Index Explanation 1 Multidiscclutch 2 Ventvalve 3 "Efficientvalve" 4 Inputshaft 5 Inputflange 6 Clutchhousing 7 EHPS 8 Electricalline 9 Longitudinaltorquedistribution(LMV)controlunit
ThelongitudinaltorquedistributionintheF48distributesthedrivetorquevariablytothefrontaxleand rearaxle.Itcomesfromtheindustrialmodularsystemofthe5thgenerationoftheHaldexsystemfrom BorgWarner.
24 F48Powertrain 4.xDrive
BoththelongitudinaltorquedistributioncontrolunitandtheEHPSpumpunitaresecuredattheside atthetransmission.
Thelongitudinaltorquedistributionclutchisintegratedintherearaxledifferential.Theinputshaftis drivenbythepropellershaftviatheinputflange.Theoutputflangedrivesthedifferential,depending onrequirements.
25 F48Powertrain 4.xDrive
4.2.4.Systemwiringdiagram
F48systemwiringdiagramforlongitudinaltorquedistribution
26 F48Powertrain 4.xDrive
Index Explanation 1 DigitalMotorElectronics(DME) 2 ElectronicPowerSteering(EPS) 3 DynamicStabilityControl(DSC) 4 Powerdistributionbox,passengercompartment 5 BodyDomainController(BDC) 6 K-CANterminator 7 Actuator,longitudinaltorquedistribution 8 Longitudinaltorquedistributioncontrolunit(LMV)
4.3.Function
4.3.1.Longitudinaltorquedistribution
F48clutch,longitudinaltorquedistribution
27 F48Powertrain 4.xDrive
Index Explanation 1 Inputflange 2 Inputshaft 3 Ventvalve 4 Workingpiston 5 Axialneedlebearing 6 Axialneedlebearing 7 Outputflange 8 Multidiscclutch 9 "Efficientvalve"
Dependingonthedrivingsituation,thelongitudinaltorquedistributioncandirectsomeofthedriving power(uptomaximumtorqueof1300 Nm)totherearaxle,sometimesbeforethewheelsevenspin.
TheDSCsendsinformationabouttheclutchtorquetobeadjustedtotheBDCviaFlexRayandto thelongitudinaltorquedistributioncontrolunitviatheK‑CAN3.Thelongitudinaltorquedistribution controlunitcontrolsthespeedoftheEHPSusingpulse-widthmodulations.Dependingonthespeed, theEHPSappliesanoperatingpressureof0to 40 bartotheclutchlongitudinaltorquedistribution.
Thepressureisnotmeasuredbyapressuresensor,butcheckedviaavoltage/currentcomparison.
Indrivingsituationsinwhichthefour-wheeldriveisnotrequired,thesystemswitchesto"Efficient mode".The"Efficientvalve"lowerstheoillevelintheclutch,thusreducingthesplashinglosses.Ifthe four-wheeldriveisrequiredagain,themaximumtorquecanbeprovidedwithin250 ms.Thespring- loaded"Efficientvalve"isoperatedbytheoilpressure.
Adaptations,whichmonitorthesystembehaviorandensurepositionprecision,areconstantly performedinthelongitudinaltorquedistributioncontrolunit.Acalibrationisperformedonceduring thedrivingcycle(terminal15ON)andstored.
Togetherwiththecalibration,asystemventilationisalsocarriedout.Thepressureisincreasedbriefly toapproximately45 barinordertoopentheventvalve.Theventilationprocedureguaranteesquick pressurebuild-upineveryregulatingsituation.
28 F48Powertrain 4.xDrive
4.3.2.Operatingstrategy
Theoperatingstrategyensuresthatthefour-wheeldriveisoperatedasrequiredandinanenergy efficientmanner.Thetractionrequirementisdetectedinaproactivemannerandthedrivetorque redirectedaccordingly.
Inmostdrivingsituationsonlythefrontwheelsaredriven.Onlyincertainsituationsissomeofthe drivetorquealsotransmittedtotherearwheels.Thedistributionofthedrivetorquebetweenthe frontandrearwheelsisdefinedbytheDSC.Thefollowingcriteriaaretakenintoaccount:
• Speed • Lateralandlongitudinalacceleration • Brakecontrol • Steeringangle • Wheelspeeds • Vehiclelongitudinalinclination • Pedalsensorposition • Activedrivingprogram(SPORT,COMFORT,ECOPRO) • DSCstatus(DSCactivated/deactivated,DTCactivated/deactivated)
Dependingonthedrivingsituation,someofthedrivetorqueistransmittedtotherearwheels. Theexactratioofthetorquedistributionisdependentontheactivationofthemultidiscclutch, aswellastheslipofthewheels.Somefactorsontheactivationofthemultidiscclutcharelistedbelow.
Thefour-wheeldriveisactivatedinthefollowingsituations,iftherearenoothercriteriapresentwhich preventthis:
• Understeeringvehicle • Increaseddifferenceinspeedbetweenfrontandrearwheels • Largevehiclelongitudinalinclination(e.g.oninclines) • Kick-downposition • Sportydrivingstyle • Respectiveenvironmentalconditions,roadwayconditionsandtypeofterrain
Thefour-wheeldriveisswitchedoffinthefollowingsituations,iftherearenoothercriteriapresent whichpreventthis:
• Largesteeringangleanddrivingspeeds • Strongbraking(ABS)
Toassesstheroadconditionandthusforeffective,proactivelongitudinaltorquedistribution,the coefficientsoffrictionbetweenthetiresandroadwayarecalculatedbytheDSC.Thewheelslip, aswellasthelongitudinalandlateralacceleration,areevaluated.
29 F48Powertrain 4.xDrive
IfwheelspeedinformationreceivedbytheDSCsuggestsdifferenttirerollingcircumferencesofthe wheels(e.g.fortireswithvaryingdegreesofwear),themultidiscclutchisnolongerclosed100 %. Differencesinspeed,resultingfromdifferentwheelspeedsatthefrontandrearaxle,arereducedin thiscaseviathemultidiscclutch,sothathightorquesarenottransmittedtothedrivetrain.
Asthemultidiscclutchisnotclosed100 %inthissituation,themaximumtransmittabledrivetorque totherearaxleisreduced.
4.4.NotesforService
• Thepropellershaftmustberemovedwhenworkingonthebraketeststand. • Whenworkingonthebraketeststand,all-wheeldrivevehicle-specificpointsdonothavetobe observed(theteststandmodeforcheckingthebrakesystemisautomaticallydetected). • Thevehiclecannotbetowedawayifonlyoneaxleisraised. • Boththeangulargearboxandtherearaxledifferentialhaveanoilfillingthatlaststheentire servicelifeoftheassembly. • Usingthediagnosissystem,boththemechanicsandthetightnessoftheEHPScanbe checked(herethepressureischeckedviaavoltage/currentcomparison). • Inordertoremovetheangulargearbox,thestartermotoralsohastoberemoved. • Similartothepreviousall-wheeldrivesystem,tireswithverydifferenttreaddepthscannotbe usedatthefrontandrearaxle. • Themaximumpermissibledeflectionangleofthepropellershaftcannotbeexceeded.
30 F48Powertrain 5.OutputShaft,Front
F48Outputshafts,front
Index Explanation B F48withfour-wheeldrive 1 Outputshaft,frontleft 2 Intermediateshaft 3 Outputshaft,frontright
Theleftoutputshaftisdesignedasasinglepiece.Therightoutputshaftconsistsofanintermediate shaftattheengineandtheactualrightoutputshaft.Bothoutputshaftsareroughlythesamelength andhavesimilartorsionalrigidity.
Thefrontoutputshaftsaredesignedaccordingtothemaximumtransmittabletorque,inorderto achieveminimalcomponentweight.
Thetransmission-endtripodjointsoffsetdifferencesinlengthanddeflectionangles,thewheel- sidefixedballjointsonlyoffsetsthedeflectionangles.Theinterfacesforthetransmissionorthe intermediateshaftaredefinedasajournalsolutionandaredesigneddependingontherespective transmission.Theinterfaceforthewheelsisdesignedasaspurgearingsolutionandisidentical forallsizes.
31 F48Powertrain 5.OutputShaft,Front
Comparisonoffrontoutputshaftsforvehicleswithfour-wheeldrive:F25–F48
Index Explanation A F25 B F48 1 Outputshaft,front 2 Angulargearbox 3 Transmission 4 Outputshaft,front 5 Oilsump 6 Frontaxledifferential
Duetothetransversalinstallationoftheengineandtransmission,intheF48thefrontoutputshaftsno longerhavetobeguidedbytheoilsump,asforexampleintheBMW X3 xDrive.Invehicleswithafour- wheeldrive,however,thefrontrightoutputshaftisguidedbytheangulargearbox.
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